AdWords is an auction-based platform, they do not set the CPC prices, your competitors do.
It’s not unusual to see the minimum bid for 1st-page placement to increase whenever a new advertiser enters the auction. When you bid high enough to get onto the 1st page of results you have effectively pushed one of your competitors off of the first page, which triggers a bidding war to get back onto the 1st page. prices will rise until at least one advertiser gives up on the idea of having ads on the 1st page of search results. You literally have to get at least one advertiser to give up on the idea of having ads on the 1st page of Google results.
Also, you might want to pay attention to your Quality Scores. Your CPC costs will go higher if your Quality Scores are dropping, even if your competitors have not adjusted their bids.
